When a User Equipment (UE) hands over, after the UE hands over to a destination side E-UTRAN Node B (eNB), the UE needs to adopt a new security algorithm configuration; however, for a scenario of UE handover failure, the UE will initiate a re-establishment request and fall back the security algorithm to an old security algorithm (that is, the security algorithm used by a source side eNB); therefore, as mentioned in the related art, when the UE hands over, the source side eNB needs to transfer the security algorithm thereof to the destination side eNB for being used under a scenario of radio link re-establishment.
However, in the related art, transferring the security algorithm of the source side eNB to the destination side eNB is mentioned only, which is used in the potential scenario of radio link re-establishment, and specific scenarios of radio link re-establishment are not distinguished; however, there are a variety of scenarios of radio link re-establishment; some of the scenarios of radio link re-establishment are not caused by the UE handover failure; and in this scenario, the problem of fallback process failure will occur based on the security algorithm of the UE falling back to the old security algorithm.
For example, in a scenario of non-competition handover, the UE receives an Msg 2 (a randomly accessed second message), at the moment, the UE considers that the handover succeeds; however, due to the quality problem of a radio link, when a re-configuration complete message is sent to the destination side eNB, Radio Link Control (RLC) layer at a user surface of the UE exceeds the maximum times of re-transmission, and at the moment, the UE could also initiate the re-establishment request to the destination side eNB; according to the related art, since the destination side eNB does not receive the re-configuration complete message, the destination side eNB considers that the handover does not succeed, at the moment the security algorithm of the UE will be updated to the old security algorithm based on receiving the re-establishment request; however, at the moment, since the UE considers that the handover succeeds, the security algorithm used by the UE has been a new security algorithm, but because of the failure of sending the re-configuration complete message to the destination side eNB, the UE sends the re-establishment request to the destination side eNB, which is not caused by the UE handover failure in a real sense; therefore, the security algorithm fallback process performed by the destination side eNB is bound to fail.
In the related art, since the security algorithm fallback process is wrongly performed in the process of radio link re-establishment, thereby it results in the problems of radio link re-establishment failure and a low success rate of the radio link re-establishment.